400/4 main bearing shells

[Matt_Harrington]

Looking at my engine in many pieces, am I right in thinking that if I can find no distinguishing marks on the existing bearing shells, then I need to reassemble the crankcases and then use a bore gauge to find the diameter of the bore in which the shells fit? That measurement together with the journal diameter should then allow me to purchase the correct shells (?). Or is there a better way?

[Oddjob]

Check the edges of the shells Matt, sometimes if you're lucky you'll find the old colour still on there. Ignore the stamping on the back of the shells, those are production marks, IF you can find any shell with a colour still on it then you can use the production marks with a reasonable degree of certainty. Any with the same exact markings will be the same colour, they have come out of the same box in the factory so should in theory be the same colour.

On the back of the crankcase, bottom section, are 5 letters stamped into the metal, these are the codes for the diameter of the journals, those are a good start. On the crank are markings that show what diameter the main and big end journals are, numbers for main and letter for big ends, same for the rods, a letter and a number, number is diameter of the journal and letter is the weight code, these will all be the same letter to balance the crank.

Try that.

[McCabe-Thiele (Ted)]

A starting point is the crankcase codes on the case itself the 5 letter on the rear -post them here for a starting point advice.

Ken has replied. Before me. I found the crank markings on the webs difficult to find but did eventually find them - they were almost like a dark shadow that did not photograph easily if at all.

[Matt_Harrington]

Mmm, cases are off being cleaned and will report back when I have them in my grubby mits! Ken, I'll double check the shells again but I'm sure I couldn't see any colour markings. ....

[Oddjob]

They tend to get washed off by the oil passing over them year after year. Worth a look though, some survive.

[Matt_Harrington]

Just had a look at the shells and no markings, alas. My spare engine (which also has some issues) has the following marked on the lower case 'CCCBC'

The crank has the following markings:

Journal 1 = 2A Conrod = D3
Journal 2 = 1A Conrod = D2
Journal 3 = 1A Conrod = D1
Journal 4 = 1A Conrod = D1

I'm not sure I'm any the wiser! 

[Trigger]

Just had a look at the shells and no markings, alas. My spare engine (which also has some issues) has the following marked on the lower case 'CCCBC'

The crank has the following markings:

Journal 1 = 2A Conrod = D3
Journal 2 = 1A Conrod = D2
Journal 3 = 1A Conrod = D1
Journal 4 = 1A Conrod = D1

I'm not sure I'm any the wiser! 

The markings and the data is for new parts and not for a worn crank. Take it to a engineer to be measured up 

[Matt_Harrington]

Trig, I have measured up the crank (my expensive digital micrometer goes to 3 decimal places). What I'm tring to resolve is whether to mic up the casing bores or whether I can use the the stamped numbers on the crankcase.

[Trigger]

Trig, I have measured up the crank (my expensive digital micrometer goes to 3 decimal places). What I'm tring to resolve is whether to mic up the casing bores or whether I can use the the stamped numbers on the crankcase.

I have only had casing journal out when the engine has sized and the shells have spun in the journal, you can see this if  the tabs are damaged and the back of the shells are scored. If this has not happened, the case journals have always been good to go 

[McCabe-Thiele (Ted)]

I am not 100% sure - 400 mains shells for casing coded C  are going to be most likely Brown or Black. Brown will be easier to find than Black.

[Oddjob]

Sorry Matt but I don't have any 400 shells, I have LOADS of 500/550 shells, more than any single place in the world I think. Well over a hundred of them. Certainly more than DS or CMS. I'm very sad 

[Matt_Harrington]

Thanks - I'll nip down to the guy doing the case cleaning tomorrow and get the letters off the case so I can get shells on order (or hunt for them!!)

Are the letter stamps in the same sequence as the journals?

So, as an example, (looking at the chart) a crank journal of 31.98mm would require a 'black' shell set for 'c'

Is it best to check with plastigauge before final assembly?

[Trigger]

always plasti gauge up everything.

[McCabe-Thiele (Ted)]

Thanks - I'll nip down to the guy doing the case cleaning tomorrow and get the letters off the case so I can get shells on order (or hunt for them!!)

Are the letter stamps in the same sequence as the journals?

So, as an example, (looking at the chart) a crank journal of 31.98mm would require a 'black' shell set for 'c'

Is it best to check with plastigauge before final assembly?

Yes the codes are in sequence from left to right so the first code is M1 etc.

Personally rather than rushing out & buying a load of shells - some might not be right.
I would mike up the crank journals then check the parts book for the possible shell codes  for your crankshaft.
I would then buy one pair of say Brown  shells if they look to be correct in the tables  then fit those in the casing codes for C and Plastigauge each C journal in turn.
The individual clearances would then tell you if the clearances are correct. Where the clearances are too large (due to wear) a Black shell would be needed.

When I did my 400 the casing codes were CAABA the shells I ended up fitting were in order M1 Black, M2 Green, M3 Green, M4 Brown, M5Green.

[Matt_Harrington]

Thanks Ted. A wise step I think. I'll re-visit this thread after a little bit more investigation.